1. Field of the Invention
The present invention relates to a magnetoresistive film, and more particularly to a magnetoresistive film having a spin valve structure.
2. Description of Related Art
A magnetoresistive element (MR element) is an element which measures a magnetic field strength and its variations by detecting changes in electric resistance of a magnetoresistive film in response to an applied magnetic field. A reproduce head (MR head) incorporating such a magnetoresistive element offers a higher magnetic sensitivity relative to conventional inductive heads, and its application to a reproduce head for hard disk drives has been widely investigated. The enhanced magnetic sensitivity of such an MR head serves to push an areal recording limits. Accordingly, increased efforts have been recently made to develop a magnetoresistive film which exhibits a high MR ratio that can be associated with the improved sensitivity.
A giant magnetoresistive element (GMR element) is known as exhibiting a high MR ratio. As one example of such a GMR element, a spin valve film is known which has a multilayer structure consisting of antiferromagnetic/ferromagnetic/nonmagnetic conductive/ferromagnetic layers. One known specific spin valve film has an FeMn/NiFe/Co/Cu/Co/NiFe multilayer structure. In the spin valve films having such a multilayer structure, the FeMn antiferromagnetic layer is strongly exchange coupled to the NiFe layer formed thereon while the NiFe layer is ferromagnetically coupled to the Co layer. As a result, one of the ferromagnetic layers is pinned by the antiferromagnetic layer. Accordingly, as a magnetization direction of another ferromagnetic layer changes in response to a varied external magnetic field, a marked change in MR ratio is caused. Thus, the enhanced magnetic sensitivity can be obtained by the use of such a spin valve film.
However, FeMn employed for the conventional antiferromagnetic layer is susceptible to corrosion, and produces corrosion pits (micropores) after passed through a polishing process generally using water. This results in an undesirable degradation of magnetoresistive characteristics.